Adding a modern, manual overdrive transmission to your classic Camaro has never been easier

We suppose back when gas was under a buck a gallon nobody really gave a damn about mileage, but today, paying over $60 to fill your tank just hurts too much to ignore. Given this economic incentive, it’s no wonder so many gearheads with TH350, TH400, and other non-overdrive transmissions are looking for a solution to drop their rpm on the highway. Yeah, they could pop in a set of uber-high gears, but then their off-the-line acceleration would take a buzz-killing hit. We’re Americans, and we want our cake and a big freaking fork to eat it with!

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Well, prepare to chow down since it’s easy to get better mileage on the highway and still retain your neck-snapping acceleration off the line. Yep, today’s lineup of overdrive transmissions makes ditching that dinosaur under your trans tunnel a snap. But what if you want a little more? What if your left foot and right hand are complaining of boredom when cruising about, or even more so while blasting through a driving event? Then what you need is a manual transmission with an overdrive, and arguably the best one out there is Tremec’s T56 Magnum. It offers the grin-plastering fun of shifting along with two full gears worth of overdrive goodness.

Internally, the Magnum is pretty much the same as what’s found in the fifth-gen SS Camaro’s TR6060 six-speed. There are triple-cone syncros on the first four gears for smoothness, and it can effectively handle over 700 lb-ft of torque. The aftermarket version of the TR6060 was designed to be swap-friendly. It has a separate bellhousing, dual speedo pick-ups to accommodate both electric and mechanical gauges, and it can handle both hydraulic and mechanical clutch systems. Of course, there’s still the matter of getting this 21st century piece of technology under your vintage Camaro, but thanks to Hurst Driveline Conversions (HDC) it’s a lot easier than it used to be.

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HDC offers a basic Magnum swap kit starting at $2,995, but we opted for their Elite kit ($4,295), which is more geared towards doing an old-school automatic to high-tech manual swap. To this we added some clutch hydraulics ($595), upgraded the bellhousing ($330) along with the clutch ($100), and tossed in one of their billet Blackjack shifters ($295). That totaled up to just over $5,600. It's not cheap, but it’s a great value for what you get.

For a car, we chose Doug Renner’s ’69 Camaro. Doug’s ride does pretty well on the autocross even with a peg-leg rear and TH350 trans, but he just knew that his outdated drivertain was holding back his awesome driving talent. Besides, cruising the highways at speed was giving his wallet a real beat down. So we gathered up our parts, stuffed them in Renner’s low-slung Camaro, and headed over the Brett Campbell’s shop, Campbell Customs, to see what’s involved in the transformation.

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1. Meet the star of our party: the Tremec Magnum six-speed transmission. With triple-cone synchronizers on gears one through four, and doubles on the rest, including reverse, it shifts like butter. On this side you can see the back-up light plug near the front, and the VSS speedo plug (with the orange cap) near the rear.

1. Meet the star of our party: the Tremec Magnum six-speed transmission. With triple-cone synchronizers on gears one through four, and doubles on the rest, including reverse, it shifts like butter. On this side you can see the back-up light plug near the front, and the VSS speedo plug (with the orange cap) near the rear.

2. The Magnums can be ordered in different ratios, but we chose the version with a 2.66 first gear and 0.63 sixth gear. If you want to run really low gears, like 4.10s, or maximized mileage on the highway, they do offer one with a 0.50 sixth gear. Either way, all Magnums share a 26-spline input and stout 31-spline output shaft. On the rear of the transmission, just below the shifter, is the reverse lockout solenoid, and just below that is the port to run a mechanical speedometer, should you choose to do so.

3. The clutch actuation parts aren’t included in the Elite kit since one can either go mechanical or hydraulic. The mechanical kit runs $350, and the hydraulic kit is a bit more at $595. Because it’s easy to install, compact, and in our opinion, simpler to deal with, we went hydraulic. The kit came with a GM throw out bearing, shorty-style Tilton master, billet firewall mounting bracket, remote reservoirs, and a bunch of fittings. The firewall bracket is especially nice since it seals the required hole in the firewall and is much stronger than the angled steel plate brackets we’ve used in the past.

4. Included in our Elite kit were all the various bits needed for installation. Having these parts, especially the electrical pigtails included, sure beats running around town trying to source them

5. We also upgraded from the standard bellhousing to this SFI-approved Quicktime scattershield. The main benefit here is that its compact design takes up less space in our already crowded trans tunnel. As bonus, it’s strong enough to contain the carnage if our clutch ever decides to fly apart. For our small-block application, the Quicktime piece added $330 to the invoice.

6. The Elite kit included a standard clutch, but Doug has plans for more power, so he opted to spend $100 and upgrade to HDC’s Competition clutch. This uses a Ram 900 series friction material in conjunction with increased clamp load pressure plates for improved holding power. Combined with the billet steel flywheel, this setup is good for up to 625 hp.

7. When it comes to transmission conversions, one key item that can make or break the install is the crossmember. The powdercoated one supplied by HDC was specifically designed for first-gen Camaros. Constructed from 0.120-inch wall carbon-steel tubing, it’s certainly strong enough, but it’s also compact, which really helps when it’s time to install an exhaust system.

8. Let’s face it; if you can’t figure out how to remove the stock transmission, you most likely shouldn’t be installing the new one. Once Brett Campbell, owner of Campbell Customs, had all the bolts holding the TH350 removed, he lowered the automatic using our handy Harbor Freight transmission jack. Sure, it doesn’t extend as high as a full-on transmission jack, but with the 20 percent off coupon found in our magazine, it only cost 110 bucks.

9. The new Magnum wasn’t much bigger than the TH350 it was replacing. One area where it’s taller is near the shifter.

10. First up was to install the Quicktime scatter shield and the flywheel supplied by Hurst Driveline Conversions (HDC), using the ARP bolts in the kit. After this, we installed the pilot bearing.

11. Using the provided alignment tool, we installed the rest of the clutch and then bolted on the SFI Quicktime bellhousing. We were told that our existing starter might not clear and that we would have to get one with a smaller end, but the GM starter cleared just fine.

12.To prep the Magnum for installation, we bolted on the GM clutch master supplied in the kit. As a bonus, it came pre-bled.

13. With that, Brett was ready to slide the Magnum under the Camaro. Before installing, the shifter had to be removed or the trans wouldn’t have been able to go high enough to get the crossmember in place. To keep things from falling in, we taped off the hole, but if you’re really industrious, you could fab up a block-off plate. We also took this opportunity to pour in our Dextron III trans fluid through the shifter hole.

14. With the trans up as high as it could go, we were able to slide in the HDC crossmember and bolt it in place. We then bolted the T56 to the crossmember using the supplied Energy Suspension’s poly mount.

15. Now that the trans was supported, we went back and fully secured the bellhousing using the grade-8 hardware from the Quicktime box. The oil filter was in the way of one fastener, so we simply flipped the bolt around.

16. With the trans in place, we used a long drill bit to blast two holes in the trans tunnel—one on the left and one on the right.

17. Using these two holes and a measuring tape, we were able to mark the area of the trans tunnel that would have to be removed for the shifter. Now, some people would only want to make a small, round hole to accommodate just the shifter handle, but it’s much better to make the access hole a bit bigger than the whole shifter plate. This way you won’t have to drop the trans if you want to service or replace the shifter assembly.

18. And here’s how it looked with the hole cut and our Hurst Blackjack billet shifter in place. The Magnum ships from Tremec with a pretty good shifter, but the Hurst billet piece, a $295 upgrade, kicks it up just a bit. The main benefit is that it allows for achieving the perfect shift stick positioning—especially important if you have a center console. The short-throw design also has a very smooth feel, and it has a lower profile compared to the Tremec shifter.

19. Moving into the engine bay, we unbolted the master, pulled it forward, and then removed the power brake booster. With that done, we put the billet clutch master mounting plate in place.

20. Using the plate as a template, we made a mark and found most of it was on the OEM block-off plate, so we removed it and only had to do a little trimming near the top. You could just cut a hole in the plate, but the two screws holding it to the firewall will keep the clutch master mounting plate from sitting flush and sealing.

21. The new HDC billet plate covered up the hole nicely. Before putting it in place, we installed the Tilton clutch master and dabbed some RTV on the backside of the plate for a watertight seal.

22. With the plate in place, we could then reinstall the brake booster and master. You can also see where we mounted the clutch fluid reservoir. It doesn’t come with a bracket, but Brett was able to fab up a sweet one, because, well, it’s what he does. Another option would be to just secure it to the firewall, but with the large booster, it was a bit tight.

23. The one part not included in the HDC kit was the pedal assembly, so we called National Parts Depot and ordered up a set (PN C-4625-2A, $74.95).

24. Under the dash, Brett simply unbolted the old single brake pedal and replaced it with the new assembly. He then used the supplied adjustable clevis to attach the clutch master pushrod to the new clutch pedal, making sure that it was adjusted to the proper distance outlined in the instructions from HDC.

25. With that done, we finished up the clutch section by attaching the supplied braided hose to the Tilton clutch master and then plugged it into the slave cylinder on the Magnum.

26. In a stroke of genius by Tremec, the Magnum was designed to accommodate both electronic and mechanical speedometers. Doug is still rockin’ the stock gauges, so he ponied up around $30 and HDC sent him over the necessary parts to get his speedo working. If he ever switches to an electric speedo, he would just need to seal off the port with the supplied plug.

27. The reverse lockout solenoid can be hooked up or left disconnected. If left alone, it will be a bit harder to get the car into reverse since the solenoid won’t be able to do its thing. If you decide to connect it, less effort would be needed to get the shifter into the reverse spot. We decided to hook it up by wiring it into the brake light circuit. We wired it in parallel since wiring it up in series will cause the brake lights to be dim, and if the solenoid fails, so will the brake lights.

28. Now it was tight, but the Magnum did fit within the Camaro’s trans tunnel. We had to “massage” it a bit in a couple of places, but the only cutting was to accommodate the shifter. We were a little concerned about the closeness of these casting protrusions on the passenger side. We talked with a tech at Tremec and got the “green light” to carefully trim them down a bit for extra clearance. In the back you can see the plug for the back-up lights. We simply plugged in the pigtail and tied it into the car’s reverse lights.

29. Our kit included a custom driveshaft, so once everything was in place, we measured from the tip of the output shaft to the middle of the U-joint mount on the differential. Three days later, a steel driveshaft arrived from HDC complete with Spicer slip yoke, Spicer U-joints, and straps. If you want to shave off some weight, or if you make over 500 hp, HDC can upgrade it to aluminum.

30. Back inside the interior, Brett crafted a sweet access cover for the shifter.

31. And just like that, we were done. The install took two full days and everything was included except the pedals and fluid. Some light hammer and dolly work was needed on the front of the trans tunnel but cutting was kept to a minimum. All in all, we would have to say the process was straightforward and HDC provided detailed instructions as well as good phone technical support. More importantly, Doug will have a lot more fun when he runs at the track and better mileage when he hits the highway.